I went the 9 inch route with a Versailles rear end.
What 9 inch is it that you found? If its not out of a Versailles or Granada or a 50s Ford then it is probably not the right size.
On the 9 inch measure the spring perches center to center and compare to yours.
Check out this thread for some links to info on Versailles and other 9 inch rear ends.
http://mustangforums.com/forum/class...swap-help.html
I have heard that the Explorer setup is a good way to go. I have not done that though. It also give you the 355 gears which is a good combination with a T5. Maybe someone that has done the Explorer swap will chime in.